(1) Field of the Invention
The present invention relates to a method and a system for detecting an intake air flow rate in an internal combustion engine provided with a supercharger. More particularly, the invention realtes to a technology for correcting an error in an air flow meter during an engine transition state.
(2) Related Art of the Invention
In an electronic control system for controlling a supply of an internal combustion engine, it is known to control the fuel supply amount on the basis of an intake air flow rate detected by an air flow meter. (see Japanese Unexamined Patent Publication (Kokai) No. 58-150040, Japanese Unexamined Patent Publication No. 59-49334)
In an internal combustion engine having an induction system using a normal aspiration, and when the volume between the air flow meter and a throttle valve is relative small, the air flow rate detected by the air flow meter coincides approximately with the air flow rate passing through the throttle valve.
Conversely, in an internal combustion engine having a supercharger, an amount of air in a boost chamber defined between a compressor of the supercharger and the throttle valve can be fluctuated by variations in the boost pressure during an engine transition state.
Therefore, in the internal combustion engine having a supercharger, the air flow meter detects variations of the amount of air in the boost chamber, in conjunction with the air passing through the throttle valve during the engine transition state. Therefore, the air flow rate detected by the air flow meter may be different from the amount of air to be introduced into the engine through the throttle valve, in an amount substantially corresponding to variations of the amount of air in the boost chamber.
Accordingly, during a transition state of the internal combustion engine having a supercharger, a precision of the level of detection of the intake air flow rate is lowered, to thus lower the precision of the air/fuel ratio control and possibly adversely affect the drivability and exhaust emission control.